plutils

commit 3baa91b7a8cc580469fb6e0c15673ea36998ceb2
parent f844d389f0a9897b15b65d8a07a2f2dd7bc9195d
Author: Robert Russell <robert@rr3.xyz>
Date:   Sun, 24 May 2026 19:39:34 -0700

Add topLevel

Diffstat:
M
src/PlUtils/DeBruijn.hs
 | 
4
++++
M
src/PlUtils/Environment.hs
 | 
2
+-

2 files changed, 5 insertions(+), 1 deletion(-)
diff --git a/src/PlUtils/DeBruijn.hs b/src/PlUtils/DeBruijn.hs
@@ -2,6 +2,7 @@ module PlUtils.DeBruijn (
     Depth (..),
     Index (..),
     Level (..),
+    topLevel,
     descend,
     idxInBounds,
     lvlInBounds,
@@ -35,6 +36,9 @@ newtype Index syn = Index {unIndex :: Nat} deriving (Show, Eq)
 -- The @syn@ phantom type parameter separates levels for different syntaxes.
 newtype Level syn = Level {unLevel :: Nat} deriving (Show, Eq)
 
+topLevel :: Depth syn
+topLevel = Depth 0
+
 descend :: Depth syn -> (Level syn, Depth syn)
 descend (Depth d) = assert (d < maxBound) "PlUtils: depth overflow" (Level d, Depth (d + 1))
 
diff --git a/src/PlUtils/Environment.hs b/src/PlUtils/Environment.hs
@@ -24,7 +24,7 @@ import PlUtils.DeBruijn
 data Environment syn v = Environment (Depth syn) (NatMap v) deriving (Show)
 
 empty :: Environment syn v
-empty = Environment (Depth 0) NatMap.empty
+empty = Environment topLevel NatMap.empty
 
 depth :: Environment syn v -> Depth syn
 depth (Environment d _) = d